Personally I would have thought any suggestion that American Democracy was suspect would make the case for possessing arms. The aim of most contributing here is to drastically reduce the number of arms in circulation.
1100 alleged deaths by police shootings would seem a very different issue to me. There is obviously a problem with the recruitment and enforcement of acceptable behaviour. Uniformed thugs with guns springs to mind. Undoubtedly a minority, but enough to taint all.
Nothing to do with civilian possession of arms.
The case with the police in the uk is different but there are numerous armed police(especially noticable in airports)
The Police Service of Northern Ireland (formerly the Royal Ulster Constabulary), Northern Ireland Security Guard Service, Ministry of Defence Police, Civil Nuclear Constabulary, Belfast Harbour Police, Belfast International Airport Constabulary, and most of the Specialist Operations units of the Metropolitan Police are all issued firearms as a matter of routine. Every force also has a Force firearms unit, with armed response vehicles.

In the US there are around 800k law enforcement officers.In the UK about a quarter of that number. Last year in the UK 5 people were killed by the police. That is a huge difference and takes some explaining.